Control of a phytoplankton bloom by wind-driven vertical mixing and light availability
Control of a phytoplankton bloom by wind-driven vertical mixing and light availability
复制标题
通过风驱动的垂直混合和光照控制浮游植物的繁殖
DOI：
10.1002/lno.11734
复制
发表时间：
2021
影响因子：
4.5
通讯作者：
Hopkins J
中科院分区：
文献类型：
--
作者：
Hopkins J
控制浮游植物生长速率和生物量积累的物理和生物过程的平衡在文献中受到广泛争论，特别是在冬春季节期间。在这里，我们表明，在温带陆架海中，主动混合的表层深度的变化是主要的阶次控制。在春季开花高峰之前的两周内，我们观察到两种不同的情况：首先，白天在真光带内生长，并在夜间通过对流混合将新的生物量重新分配到季节性的重斜层；然后，更快速的生物量积累被困在较浅的、风驱动的活跃混合层中，该混合层与下面的重斜层脱钩。我们使用海洋滑翔机对西北欧洲大陆架凯尔特海的水华进行了观测，包括对湍流动能耗散的测量。由我们对耗散和入射辐照度的测量驱动的一维浮游植物生长模型复制了观察到的水华，并强化了这样的结论：介导光可用性的物理过程是关键。云量的日常变化和浮游植物适应光环境的能力也是决定生长速率和生物量峰值时间的重要因素。我们的结果强调了耦合水动力生态系统模型中精确的湍流混合参数化的必要性。我们的研究结果适用于风驱动混合可以改变养分和光利用率的任何地区，特别是在北半球的亚极地架上，那里的光而不是养分通常是浮游植物生长的限制因素。
The balance of physical and biological processes governing phytoplankton growth rates and the accumulation of biomass is widely debated in the literature, notably during the winter–spring transition. Here we show, in a temperate shelf sea that variability in the depth of the actively mixing surface layer is the leading order control. During a 2‐week period preceding the peak of the spring bloom we observe two distinct regimes; first, growth within the euphotic zone during the day and re‐distribution of new biomass to the seasonal pycnocline at night by convective mixing; then, more rapid biomass accumulation trapped within a shallower, wind‐driven actively mixing layer that was decoupled from the pycnocline below. Our observations of the bloom in the Celtic Sea, Northwest European Shelf, were made using ocean gliders and include measurements of the dissipation of turbulent kinetic energy. A 1‐D phytoplankton growth model driven by our measurements of dissipation and incident irradiance replicates the observed bloom and reinforces the conclusion that physical processes that mediate light availability were key. Day‐to‐day variability in cloud cover and the ability of phytoplankton to acclimate to their light environment were also important factors in determining growth rates, and the timing of the biomass peak. Our results emphasize the need for accurate turbulent mixing parameterizations in coupled hydrodynamic‐ecosystem models. Our findings are applicable to any region where wind‐driven mixing can modify nutrient and light availability, especially across subpolar shelves in the northern hemisphere where light rather than nutrients is typically the limiting factor on phytoplankton growth.